Many test systems exist for the testing of printed circuit boards during manufacturing. These systems generally involve some form of a "bed of nails" wherein a series of metallic pins make contact with points on a PCB. These systems may automatically test resistance, capacitance etc. or may inject signals to test for shorted or unconnected electrical paths.
However, "in-house" testing, or testing during manufacturing, is only one part of PCB testing. Testing of PCBs is also required during research and development, and often after the product has been sold and installed in customer premises. In such situations a portable and easily alterable in-circuit test system is required. Typically testing in such situations employs oscilloscopes, logic analyzers, and/or data scopes. These instruments are carried to the laboratory or into the field and are connected to the circuit board via test clips connected to wires attached to the test equipment. Such a technique has worked well on simple PCBs involving very few integrated circuits, and wherein the ICs have been in the form of dual in-line packages such as Intel's part #74LS74. A dual in-line package, due to its construction, allows the test clips attached to the test equipment to be easily connected. However, current technology is leading to PCBs having a high density of ICs. These ICs may be in the form of dual in-line, flat pack, or surface mount technologies. In the case of dual in-line packages, it is very often difficult to attach all the test clips required to perform a reasonable circuit test due to the reduced open board area. The use of flat pack or surface mount technologies makes it difficult, if not impossible, to connect test clips to their interconnection leads. One problem of testing numerous points on a PCB, as may be required, is the resulting congestion of test probes and their interconnection leads making changes difficult and entangling equipment and interconnection leads.
Different systems have been proposed to overcome the problems of testing these new, high density circuit packs. One such system is described in U.S. Pat. No. 4,362,991 issued Dec. 7, 1982 in the name of Joseph C. Carbine entitled "Integrated Circuit Test Probe Assembly". In that patent a system is described where any IC on a PCB may be tested. However, the system of that patent is limited to the testing of PCBs employing flat pack IC packages. Additionally, the system of that patent only allows the testing of a single IC at one time; it does not allow for the testing of several ICs or other components, such as resistors or capacitors, or signal test points that may be part of the design of the PCB.